Edition: BP 2025 (Ph. Eur. 11.6 update)
Kaolin Oral Suspension
DEFINITION
Kaolin Mixture is an oral suspension containing 20% w/v of Light Kaolin or Light Kaolin (Natural) and 5% w/v each of Light Magnesium Carbonate and Sodium Bicarbonate in a suitable vehicle with a peppermint flavour.
It should be recently prepared unless the kaolin has been sterilised.
The mixture complies with the requirements stated under Oral Liquids and with the following requirements.
Content of magnesium, Mg
1.04 to 1.25% w/w.
Content of sodium bicarbonate, NaHCO3
4.05 to 4.65% w/w.
TESTS
Acid-insoluble matter
13.8 to 18.4% w/w when determined by the following method. Dry and ignite the residue reserved in the Assay for magnesium to constant weight at red heat.
ASSAY
For magnesium
To 3 g add 15 mL of water, make acidic to litmus paper by the cautious addition of 2M hydrochloric acid, boil for 5 minutes, replacing the water lost by evaporation, cool and filter the supernatant liquid. Boil the residue with 20 mL of water and 10 mL of 2M hydrochloric acid, cool, filter through the same filter and wash the residue with water until the washings are free from chloride. Reserve the residue for the test for Acid-insoluble matter. Dilute the combined filtrate and washings to 100 mL with water. To 20 mL add 0.1 g of L-ascorbic acid, make slightly alkaline to litmus paper with 5M ammonia and add 10 mL of triethanolamine, 10 mL of ammonia buffer pH 10.9 and 1 mL of a 10% w/v solution of potassium cyanide. Titrate with 0.05M disodium edetate VS, using mordant black 11 solution as indicator, to a full blue colour. Each mL of 0.05M disodium edetate VS is equivalent to 1.215 mg of Mg.
For sodium bicarbonate
Boil 10 g with 100 mL of water for 5 minutes, filter, boil the residue with 100 mL of water for 5 minutes and filter. Combine the filtrates, cool and titrate with 0.5M hydrochloric acid VS using methyl orange-xylene cyanol FF solution as indicator. Add 10 mL of ammonia buffer pH 10.9 and titrate with 0.05M disodium edetate VS using mordant black 11 solution as indicator. After subtracting one-fifth of the volume of 0.05M disodium edetate VS, each mL of 0.5M hydrochloric acid VS is equivalent to 42.00 mg of NaHCO3
